Some widely used mowers, chain saws, and other small-sized machines, which are one type of engine-equipped machine, are equipped with a two-cycle engine that produces power by burning a composite fuel obtained by mixing in advance gasoline or any other suitable fuel with a lubricating oil for lubricating parts (members) of the engine.
In a two-cycle engine of this type, a composite fuel not only produces power when burned but also lubricates members of the engine (see Patent Document 1, for example).
In a two-cycle engine, there is always a need to reduce the ratio of the lubricating oil to the composite fuel. In a conventional two-cycle engine, however, reducing the amount of lubricating oil disadvantageously leads to insufficient lubrication of sliding surfaces of a cylinder or a cylinder liner and a piston and peripheral members thereof, causing the piston and the peripheral members thereof, which make reciprocating motion in the cylinder or the cylinder liner, to seize.
The problem described above is not limited to a two-cycle engine having a structure using a composite fuel obtained by mixing a fuel with a lubricating oil in advance. For example, in a two-cycle engine in which a fuel and a lubricating oil are separately supplied to a crankcase, the problem described above similarly occurs as long as the engine is configured to use an air-fuel mixture obtained by mixing the fuel with the lubricating oil to produce power and lubricate parts of the engine.
Patent Document 1
Japanese Patent Laid-Open No. 2007-231887